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Forecast Surplus Baseload Generation Report

Surplus Baseload Generation (SBG) occurs when electricity production from baseload facilities (such as nuclear, hydro and wind) is greater than Ontario demand. Currently, there are limited options to lower output from baseload generators in order to maintain the balance between supply and demand. The reports below provide hourly forecasts of when SBG is calculated to take place over the following 10 days. The purpose of the report is to support Market Participants to make decisions about scheduling their resources, with the potential to help alleviate the impact of SBG.

Report Format:  XML 
Forecast Surplus Baseload Generation Reports
Mon Tue Wed Thu Fri Sat Sun
          Oct 11 Oct 12
Oct 13 Oct 14 Oct 15 Oct 16 Oct 17 Oct 18 Oct 19
Oct 20 Oct 21 Oct 22 Oct 23      

NEW: Revised SBG Forecast Reporting:
In consultation with stakeholders, the IESO has developed a new 10 day SBG Forecast Report that is designed to provide a more effective information tool for market participants, by incorporating the following enhancements:

  • As SBG forecasts do not include exports in the calculation, a new column has been added which shows the expected export capacity to provide an indication of the amount of SBG that may be alleviated through exports
  • This new forecast will now be published on weekends and holidays as well as on business days
  • An improved forecast in days 1-4 through additional information on hydro generation and by incorporating the IESO’s new centralized wind forecasting results
  • The introduction of Minimum Generation Alerts up to four days in advance that also appear in the Security and Adequacy Assessments (SAA) and System Status Reports (SSR)

The SBG forecasts consider near-term forecasts for hydro-electric, wind, and other baseload generation as well as weather conditions which impact demand.  As such, the IESO endeavours to provide as much information in advance of the relevant day so that market participants are aware of potential SBG conditions and can plan their business and respond appropriately.  For example, large volume consumers may choose to increase production during these periods to take advantage of lower prices, while generators may consider off-line maintenance activities.

For longer-term forecasts, participants should refer to Table A9 of the current 18-month Outlook which provides an assessment of forecast weekly minimum demands and expected baseload generation for the next year and a half. This table has two columns that contain data for Ontario’s normal weather overnight minimum demand forecast, based on economic forecast drivers and historical usage patterns:

  • The Weekly Minimum Demand MW represents the absolute lowest hourly demand for the week. This value typically occurs during the overnight period of a weekend or holiday.
  • The Weekly Highest Minimum Demand MW represents the highest overnight minimum demand for the week. This value typically occurs during the overnight period of weekday, generally on a Wednesday night.

Note that Minimum Demands are based on typical weather patterns so seasonally abnormal hot or cold weather may result in a significant variation from normal.

Participants are advised to refer to the difference between the Weekly Minimum Demand MW and the Baseload Generation MW columns as an indicator of Ontario’s exposure to future Surplus Baseload Generation risk. 


NEW: Minimum Generation Alerts:
When conditions warrant, the IESO will communicate a Minimum Generation Alert or Event through the SAA, SSRs and in the SBG Forecasts.*   Here is an overview of the forecast conditions that would trigger an Alert or Event.


Forecast Condition

Minimum Generation Status

3-4 days out

Forecast SBG will exceed the forecast of expected exports for four or more contiguous hours.      


1-2 days out

Forecast SBG will exceed the forecast of expected exports for two or more contiguous hours.       



Pre-dispatch shows a baseload generation manoeuvre of 50 MW or more.



Baseload generation manoeuvre is imminent or in progress

Event (only applied to the SSR)

* Note that the IESO will cancel a Minimum Generation Alert if conditions change and the criteria are no longer met.


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